To improve properties of alloy plating films, composite plating films are developed in which fine particles such as resin particles are dispersed in their alloy matrix phases. For example, as described in Patent Literature 1 and 2, composite plating films are known in which fluorine resin particles are dispersed in Ni—P alloy matrix phases. These composite plating films may have, for example, improved water-repellent property and oil-repellent property.